/* ── Shared design tokens + course sidebar (single source of truth) ── */
@import "tokens.css";
@import "course-nav.css";

/* ── Reset & base ── */
* {
  box-sizing: border-box;
}
html {
  background: #0c0e12;
  scroll-behavior: smooth;
}
body {
  margin: 0;
  background: linear-gradient(180deg, #0c0e12, #0f1115 240px);
  color: var(--ink);
  font:
    16px/1.65 -apple-system,
    BlinkMacSystemFont,
    "Segoe UI",
    Inter,
    Roboto,
    Helvetica,
    Arial,
    sans-serif;
  -webkit-font-smoothing: antialiased;
}

/* ── Sleek page scrollbar (matches the course sidebar) ── */
html {
  scrollbar-width: thin;
  scrollbar-color: #2a2f3a transparent;
}
html::-webkit-scrollbar {
  width: 10px;
}
html::-webkit-scrollbar-track {
  background: transparent;
}
html::-webkit-scrollbar-thumb {
  background: #2a2f3a;
  border-radius: 8px;
  border: 2px solid #0c0e12;
}
html::-webkit-scrollbar-thumb:hover {
  background: #475063;
}

/* ── Layout ── */
.wrap {
  max-width: 860px;
  margin: 0 auto;
  padding: 48px 24px 96px;
}
header.hero {
  border-bottom: 1px solid var(--line);
  padding-bottom: 28px;
  margin-bottom: 36px;
}

/* ── Typography ── */
.kicker {
  font-size: 13px;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--accent);
  font-weight: 700;
}
h1 {
  font-size: 34px;
  line-height: 1.15;
  margin: 0.35em 0 0.2em;
  letter-spacing: -0.02em;
}
h2 {
  font-size: 23px;
  margin: 48px 0 6px;
  letter-spacing: -0.01em;
}
h2 .num {
  color: var(--accent);
  font-variant-numeric: tabular-nums;
  margin-right: 0.4em;
}
h3 {
  font-size: 17px;
  margin: 26px 0 6px;
}
p {
  margin: 0.55em 0;
}
.sub {
  color: var(--muted);
  font-size: 16px;
  max-width: 62ch;
}

/* ── Links ── */
a {
  color: var(--accent);
  text-decoration: none;
  border-bottom: 1px solid #2f3c54;
}
a:hover {
  border-color: var(--accent);
}

/* ── Code ── */
code {
  background: #11141a;
  border: 1px solid var(--line);
  border-radius: 6px;
  padding: 0.08em 0.4em;
  font-size: 13.5px;
  font-family: "SF Mono", ui-monospace, Menlo, Consolas, monospace;
  color: #e6d6ff;
}
pre {
  background: #0b0d12;
  border: 1px solid var(--line);
  border-radius: 10px;
  padding: 14px 16px;
  overflow: auto;
  margin: 14px 0;
}
pre code {
  background: none;
  border: none;
  padding: 0;
  color: #d7e3ff;
  font-size: 13px;
  line-height: 1.6;
}
.tok-tag {
  color: #7ee0c0;
}
.tok-attr {
  color: #ffcf6e;
}
.tok-str {
  color: #9ad0ff;
}
.tok-com {
  color: #5a6477;
  font-style: italic;
}

/* ── Components ── */
.mission {
  margin-top: 18px;
  background: var(--panel);
  border: 1px solid var(--line);
  border-left: 3px solid var(--accent2);
  border-radius: 10px;
  padding: 14px 16px;
  font-size: 14.5px;
  color: #cdd4e0;
}
.mission b {
  color: var(--accent2);
}

.lead {
  display: flex;
  gap: 12px;
  background: var(--panel);
  border: 1px solid var(--line);
  border-radius: 10px;
  padding: 14px 16px;
  margin: 14px 0;
}
/* Multi-paragraph "Full loop" boxes: stack paragraphs vertically instead of
   letting flex turn each <p> into a side-by-side column. */
.lead:has(p + p) {
  flex-direction: column;
  gap: 8px;
}
.lead .pill {
  flex: 0 0 auto;
  font-size: 11px;
  font-weight: 800;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: #0c0e12;
  background: var(--accent2);
  border-radius: 999px;
  padding: 3px 10px;
  height: max-content;
}
.lead p {
  margin: 0;
  font-size: 14.5px;
  color: #d3dae6;
}

.tradeoff {
  background: linear-gradient(180deg, #1a1410, #171a21);
  border: 1px solid #3a2f1e;
  border-left: 3px solid var(--warn);
  border-radius: 10px;
  padding: 14px 16px;
  margin: 16px 0;
}
.tradeoff b {
  color: var(--warn);
}

/* ── Tables ── */
table {
  width: 100%;
  border-collapse: collapse;
  margin: 16px 0;
  font-size: 14px;
}
th,
td {
  border: 1px solid var(--line);
  padding: 9px 11px;
  text-align: left;
  vertical-align: top;
}
th {
  background: var(--panel2);
  color: #cfd6e3;
  font-size: 12.5px;
  letter-spacing: 0.03em;
  text-transform: uppercase;
}
td code {
  font-size: 12.5px;
}

/* ── Cards ── */
.grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 14px;
  margin: 16px 0;
}
@media (max-width: 640px) {
  .grid {
    grid-template-columns: 1fr;
  }
}
.card {
  background: var(--panel);
  border: 1px solid var(--line);
  border-radius: 12px;
  padding: 16px;
}
.card h4 {
  margin: 0 0 4px;
  font-size: 15px;
  color: #fff;
}
.card .when {
  color: var(--good);
  font-size: 12.5px;
  font-weight: 600;
}
.card p {
  font-size: 13.5px;
  color: #c4cbd8;
  margin: 0.4em 0 0;
}

/* ── Quiz ── */
.quiz {
  background: var(--panel);
  border: 1px solid var(--line);
  border-radius: 14px;
  padding: 20px 20px 8px;
  margin: 20px 0;
}
.quiz .q {
  font-weight: 600;
  margin: 0 0 12px;
  font-size: 15.5px;
}
.quiz .scn {
  color: var(--muted);
  font-size: 13.5px;
  margin: -6px 0 12px;
}
.opt {
  display: block;
  width: 100%;
  text-align: left;
  background: var(--panel2);
  border: 1px solid var(--line);
  color: var(--ink);
  border-radius: 9px;
  padding: 11px 13px;
  margin: 8px 0;
  cursor: pointer;
  font-size: 14px;
  transition: 0.12s;
}
.opt:hover {
  border-color: #3c4658;
  background: #222838;
}
.opt.correct {
  border-color: var(--good);
  background: #16241c;
}
.opt.wrong {
  border-color: var(--bad);
  background: #241618;
}
.opt .mark {
  font-weight: 800;
  margin-right: 8px;
}
.fb {
  display: none;
  margin: 6px 2px 16px;
  padding: 12px 14px;
  border-radius: 9px;
  font-size: 13.8px;
  line-height: 1.6;
}
.fb.show {
  display: block;
}
.fb.ok {
  display: block;
  background: #13241b;
  border: 1px solid #224a33;
  color: #bdf0d0;
}
.fb.no {
  display: block;
  background: #241417;
  border: 1px solid #4a2630;
  color: #f0c4cc;
}
.progress {
  font-size: 12.5px;
  color: var(--muted);
  margin-top: 6px;
}

/* ── Footer & citations ── */
.footer {
  margin-top: 48px;
  border-top: 1px solid var(--line);
  padding-top: 22px;
  color: var(--muted);
  font-size: 14px;
}
.cite {
  font-size: 12.5px;
  color: var(--muted);
}
.cite a {
  color: #8fb6ff;
}

@keyframes shimmer {
  0%   { background-position: -400px 0 }
  100% { background-position:  400px 0 }
}
.author-sig {
  margin-top: 16px;
  padding-top: 14px;
  border-top: 1px solid var(--line);
  font-size: 12.5px;
  color: var(--muted);
}
.author-sig a { font-size: 12.5px; color: #8fb6ff; border-bottom-color: #2f3c54 }
.sig-shimmer {
  background: linear-gradient(90deg, var(--muted) 30%, #fff 50%, var(--muted) 70%);
  background-size: 400px 100%;
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
  animation: shimmer 3s infinite linear;
}
.sig-shimmer a {
  -webkit-text-fill-color: transparent;
  background: inherit;
  -webkit-background-clip: text;
  background-clip: text;
}

/* ── Ask / follow-up ── */
.ask {
  background: linear-gradient(135deg, #15233a, #1a1530);
  border: 1px solid #2c3b5a;
  border-radius: 12px;
  padding: 16px 18px;
  margin: 28px 0;
}
.ask b {
  color: var(--accent);
}
.tags {
  display: flex;
  gap: 8px;
  flex-wrap: wrap;
  margin-top: 10px;
}
.tag {
  background: var(--chip);
  border: 1px solid var(--line);
  color: #aeb7c6;
  font-size: 12px;
  border-radius: 999px;
  padding: 3px 11px;
}

/* ── Misc ── */
ul.tight {
  margin: 0.4em 0;
  padding-left: 1.2em;
}
ul.tight li {
  margin: 0.25em 0;
}
.big-q {
  font-size: 15px;
  color: #dfe5ef;
  background: #11141a;
  border: 1px dashed #34405a;
  border-radius: 10px;
  padding: 12px 14px;
  margin: 10px 0;
}

/* ── Lesson navigation ── */
.lesson-nav {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 8px;
  padding: 10px 0;
  border-bottom: 1px solid var(--line);
  margin-bottom: 32px;
  font-size: 13px;
}
.lesson-nav.bottom {
  border-top: 1px solid var(--line);
  border-bottom: none;
  margin-top: 48px;
  margin-bottom: 0;
}
.nav-btn {
  background: var(--panel2);
  border: 1px solid var(--line);
  border-radius: 6px;
  padding: 6px 14px;
  color: var(--accent);
  cursor: pointer;
  text-decoration: none;
  white-space: nowrap;
  font-size: 13px;
  transition: background 0.15s;
}
.nav-btn:hover {
  background: #252b38;
  text-decoration: none;
}
.nav-btn.disabled {
  color: var(--muted);
  cursor: default;
  pointer-events: none;
}
.nav-center {
  font-size: 12px;
  color: var(--muted);
  text-align: center;
  flex: 1;
}

/* ── Responsive ── */
@media (max-width: 700px) {
  .wrap {
    padding: 32px 16px 72px;
  }
  h1 {
    font-size: 26px;
    letter-spacing: -0.01em;
  }
  h2 {
    font-size: 20px;
  }
  h3 {
    font-size: 16px;
  }
  .lesson-nav,
  .lesson-nav.bottom {
    flex-wrap: wrap;
    gap: 6px;
  }
  .nav-center {
    order: 3;
    width: 100%;
    text-align: center;
    flex: none;
    padding-top: 2px;
  }
  .nav-btn {
    font-size: 12px;
    padding: 5px 10px;
    white-space: normal;
  }
  pre {
    font-size: 11.5px;
  }
  table {
    display: block;
    overflow-x: auto;
    -webkit-overflow-scrolling: touch;
    font-size: 13px;
  }
  th,
  td {
    padding: 7px 8px;
  }
  .pick2-grid,
  .grid3-cols {
    grid-template-columns: 1fr;
  }
  .pick2-card {
    padding: 14px;
  }
  .frow {
    flex-wrap: wrap;
    gap: 8px;
  }
  .ab {
    min-width: 0;
    flex: 1 1 calc(50% - 5px);
  }
  .viz-compose,
  .lb-viz,
  .flow-diagram,
  .tl-wrap,
  .scale-viz-inner,
  .cjsplit {
    overflow-x: auto;
    -webkit-overflow-scrolling: touch;
  }
  .lead {
    flex-direction: column;
    gap: 8px;
  }
}
@media (max-width: 480px) {
  .wrap {
    padding: 20px 12px 56px;
  }
  h1 {
    font-size: 22px;
  }
  h2 {
    font-size: 17px;
  }
  body {
    font-size: 15px;
    line-height: 1.7;
  }
  .kicker {
    font-size: 11px;
  }
  .sub {
    font-size: 14px;
  }
  .mission {
    padding: 11px 13px;
    font-size: 13.5px;
  }
  .lead {
    padding: 12px 13px;
    gap: 10px;
  }
  .lead p {
    font-size: 13.5px;
  }
  .tradeoff {
    padding: 11px 13px;
  }
  code {
    font-size: 12.5px;
  }
  pre {
    font-size: 11px;
  }
  .quiz {
    padding: 14px 12px 6px;
  }
  .opt {
    font-size: 13.5px;
    padding: 10px 11px;
  }
  .ask {
    padding: 12px 14px;
  }
  .tags {
    gap: 6px;
  }
  .tag {
    font-size: 11px;
    padding: 3px 9px;
  }
  .big-q {
    font-size: 14px;
    padding: 10px 12px;
  }
  .footer {
    font-size: 13px;
  }
  .nav-btn {
    font-size: 11px;
    padding: 4px 8px;
  }
  .card {
    padding: 13px;
  }
}